1. Field of Invention
This invention relates to volume regulating devices used in positive and negative pressure air delivery systems, specifically to centrally actuated, multiple blade butterfly type dampers commonly used in heating and air conditioning systems, to regulate air flow to a particular outlet.
2. Description of Prior Art
Air delivery or distribution systems are used for heating, ventilation and air conditioning (HVAC) requirements. These systems may consist of various sizes and types of ducts, or conduits, used to convey air to or from a desired area. In some cases air from a single source such as a fan or other air handling unit is distributed to multiple branch ducts, with each branch terminating at a grille, or diffuser.
A desirable feature of such a system is a volume damper at each diffuser to regulate airflow. This ability allows one to adjust for personal comfort, or a change in airflow requirements for the conditioned space. It is most convenient if this damper is integral with the diffuser or outlet. This allows easy access by the occupants, and pre-assembly at the factory to save labor in the field. In cooler climates it is also desirable to have the ability to completely stop the airflow at the diffuser when the system is not in use, such as in a dedicated air conditioning system during winter. Currently available dampers designed for such systems are not very airtight in the closed position. This results in unwanted airflow through the system due to temperature differential, causing drafts, and condensation. In particular, ductwork systems installed in attics are prone to this problem, especially in the presence of moist air.
Airtight dampers and valves have been produced for many purposes, but most are not suitable for HVAC systems due to cost, weight, or complexity. An argument could be made that any suitable damper could be made air tight by gasketing all moving parts. However complex shapes with multiple mating surfaces and interruptions require complex shaped, and/or multiple gaskets and are difficult to seal effectively. Also, for a damper to be accessible from the living space and be integral with the diffuser, an actuation mechanism may exist within the air stream. This complex mechanism must therefore be gasketed, which can add friction, obstruction to smooth movement, and further complexity. U.S. Pat. No. 5,979,053 by Shaeffer, et al describes an diagonally offset damper blade to achieve a seal around the blades perimeter, independent of shaft seals. U.S. Pat. No. 4,489,917 by Baumann achieves the same using a cone shaped blade. While both designs have merit for their intended use, neither will allow for a convenient actuator parallel with the flow of air to allow access through the diffuser.
Accordingly, several objects and advantages of the present invention are:
(a) to provide a butterfly type volume damper with an actuation mechanism accessible through an air diffuser, and from the living space.
(b) to provide a means to seal the damper actuating mechanism to achieve minimal air leakage in the closed position.
(c) to provide for a sealing means along the perimeter of the damper.
(d) to provide a damper configuration or shape which allows for a continuous, uninterrupted sealing means, or gasket without having to conform to complex shapes and curves.
(e) to create a simple economical method of damper manufacture with a minimal amount of moving parts.
Further objects and advantages will become apparent from consideration of the ensuing description and drawings.